The goal of this proposal is the development and in vivo validation of advanced MRI techniques designed to provide a comprehensive anatomic and functional evaluation of the kidney in a single examination, and the subsequent application of these techniques to the diagnosis of patients with renal artery stenosis and chronic renal ischemia. Detailed anatomic information will be obtained through further development of successful existing techniques for ultrafast contrast-enhanced magnetic resonance angiography (MRA). In addition to high- resolution imaging of the renal vasculature, the MRA sequence will be employed to obtain 3- dimensional images of the renal parenchyma; accurate depiction of the renal cortex and medulla will also be achieved by correlation imaging, and volumes of these zones will be rapidly calculated using semi-automated computerized techniques. Building on our successful techniques for the in vivo measurement of renal blood flow with breathing- resolved cine phase-contrast techniques using spiral k-space trajectories, we will design and validate a sequence for the determination of the extraction fraction (EF) of gadolinium-DTPA from the kidney. EF will be measured by determining systemic and renal venous T1 values, which will allow determination of the difference in gadolinium-DTPA concentration. Using these EF determinations and renal blood flow values determined by our existing spiral phase-contrast techniques, we will compute single-kidney values of glomerular filtration rate (GFR), the standard measure of renal function. All the above techniques, following validation in vivo in normal pigs, will form the components of a single comprehensive MRI exam which will be used to diagnose patients with chronic renal ischemia. The utility of the comprehensive exam will be determined by correlating pre- intervention MRI-determined parameters with both clinical outcome measures and post-intervention MRI-determined parameters.